Pseudomonas aeruginosa is an important cause of severe central corneal ulceration. A new experimental model of keratitis was developed in guinea pigs. This model is suitable for quantitative evaluation. Animals are infected intracorneally with bacteria. The natural history of the untreated infection will be determined by inspection, slit-lamp examination, light and electron microscopy, and determination of the number of bacteria in the cornea. Optimal antibiotic therapy will be determined. The influence of corticosteroids and enzyme inhibitors on therapy will be determined. The effect of active and passive immunization will be evaluated.